1. Field of the Invention
The present invention relates to an improvement in aqueous alumina sol, particularly to a stable aqueous sol of amorphous alumina having a uniform length of 200 to 500 millimicrons and a controlled thickness of 20 to 100 millimicrons, and the method for preparing the sols.
2. Description of Prior Art
Japanese patent publication No. Sho 32-3367 (1957) discloses a method for preparing an aqueous sol of alumina by a process comprising reacting metallic aluminum directly with water in the presence of an acid such as inorganic or organic.
Japanese patent laid-open publication No. Sho 60-166220 (1985) discloses methods for preparing aqueous sols of amorphous alumina in fibrous form by a process comprising adding metallic aluminum into an aqueous solution of organic acid and heating the solution at a high temperature to obtain a reaction mixture, and followed by further adding an organic acid and metallic aluminum into the reaction mixture. However, the sols obtained by the method can not give sufficient properties to products obtained by using the sols, for example, carriers for catalysts, etc.